...McCain is currently behind in most electoral college predictions by at least 100 electoral votes. The polls would have to be VERY wrong for Obama to lose.
This link provides a very brief analysis of the polling error in the 2004 election. Although G.W. Bush ened up winning the election, the polls had underestimated his electoral vote count by as much as 55.
Obama's current polling suggests a 100 electoral vote lead over McCain. It is highly unlikely that the polls are that wrong. The only question now is, how right are they about Obama's landslide?